Systematically Quantifying Neutral Wind Response Times Over the High Latitude Auroral Oval

Different from high latitude ionospheric plasma convection, which is driven by electromagnetic coupling between the magnetic field and the solar wind, the thermosphere has a number of drivers, with the main contributors being ion drag and thermal pressure gradients. Additionally, the efficiency of each of the thermospheric drivers is not well characterized, which results in a wide reported range of neutral wind response times, from tens of minutes to hours. In the current study we investigate ion-neutral coupling efficiency as a function of geomagnetic activity levels by using PFISR and collocated Scanning Doppler Imager data for ion velocity and neutral winds, respectively. Compared with Fabry-Perot Interferometers, SDIs measure winds from tens of looking directions simultaneously and can track wind evolution at a cadence of 1-5 minutes, making it reliable to study fast neutral wind response. Event selection requires clear sky conditions and exhibits a change in ion velocity from one steady state to a new steady state. Using various methods, ion-neutral coupling rates are calculated and then compared to the SYM-H and AE index, which gives a measure of the ion-neutral coupling efficiency as a function of geomagnetic activity, as well as providing insight on the efficiency of the individual drivers of the thermosphere.